This invention relates to a silver halide photographic material containing a novel black and white image-forming coupler and a process of forming black and white photographic images using the photographic material. More particularly, the invention relates to a silver halide photographic material which can imagewise form a novel black dye in place of silver images, thereby the amount of silver in the photographic material is reduced, and further to a process of forming images using the foregoing silver halide photographic material.
In an ordinary process of forming black and white photographic images, a silver halide photographic material is imagewise exposed to form a latent image therein. The photographic material is then processed by an ordinary black and white developer containing an ordinary black and white developing agent such as, for example, hydroquinone, Metol, phenidone, etc. Metallic silver formed at the latent image portion is utilized as the black and white image.
At present the shortage of silver resources has become a serious problem. The tendency of at least partially substituting some materials for silver in black and white photographic images has been raised in the field of the art. One of these attempts is the replacement with a black dye.
Various processes have been proposed for the purpose. For example, the following processes are known: (1) forming a black dye image from 1,5-dihydroxynaphthalene and 2,5-dibromo-4-aminophenol as described in U.S. Pat. No. 1,939,231; (2) a process of forming a black image using a p-phenylenediamine derivative and phenol, naphthol, or an active methylene compound as described in U.S. Pat. No. 2,181,944; (3) a process of forming a black image using 3-aminopyrazolobenzimidazole as a developing agent and an active methylene compound as a coupler as described in West German Patent No. 1,158,836; (4) a process of forming a black image by color developing a mixture of couplers capable of forming yellow, magenta, and cyan dyes used usually in present color photography as described in British Pat. No. 492,518 and West German Patent No. 537,923; (5) a process of reducing the coating amount of silver by performing coloring development under the presence of color coupler and then fixing without removing silver to form a dye image and a silver image simultaneously as described in Japanese Patent Application (OPI) No. 37539/72 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application"); (6) a process of forming a black image using an m-aminophenol derivative as a coupler as described in Japanese Patent Application (OPI) No. 52725/77; and (7) a process for forming a black image using a multifunctional coupler and a multifunctional developing agent as described in Japanese Patent Application (OPI) No. 57827/77.
However, when using these methods, a high image density is not obtained for the amount of coated silver and the materials for forming images are relatively expensive. Therefore, these methods have not yet been practically used.
In addition, Japanese Patent Application (OPI) No. 9924/79 describes a method of forming a black dye using a non-diffusible type resorcin coupler. However, this method is disadvantageous because a sufficiently neutral density, that is, a deep-black color image is not obtained by the coupler as described in the foregoing patent application. Furthermore, the amount of the dye formed per unit amount of coated silver is small, which shows the reducibility of the amount of coated silver is low.